Device to device (D2D) communication has been developed for years and have been extended to include vehicle-to-anything (V2X) communication. For example, in current telecommunication specifications such as the 3rd Generation Partnership Project (3GPP) specification Release 14, the extensions for the D2D work consist of support of V2X communication. V2X communication includes any combination of direct communication between vehicles, pedestrians, infrastructures, and networks, and thus can be divided into the following four different types: Vehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P), Vehicle-to-Infrastructure (V2I), Vehicle-to-Network (V2N). V2V communication includes communication between vehicles; V2P communication includes communication between a vehicle and a device carried by an individual (for example, a handheld user terminal carried by a pedestrian, cyclist, driver, or passenger); V2I communication includes communication between a vehicle and infrastructures supporting V2X applications, such as roadside units (RSUs) which are transportation infrastructure entities; and V2N communication includes communication between a vehicle and network infrastructures such as a network terminal.
V2X communication may take advantage of a network (NW) infrastructure, when available, but at least basic V2X connectivity should be possible even in case of lack of network coverage. Providing a V2X interface based on networks (such as a Long Term Evolution (LTE)-based V2X interface) may be economically advantageous (especially because of the LTE economies of scale) and may enable tighter integration between V2I, V2P, and V2V communications, as compared to using a dedicated V2X technology. Therefore, V2I, V2P, and V2V communications can be performed via Uu interfaces or direct links therebetween (also referred to as sidelinks), while V2N communication is performed via Uu interfaces since network devices are involved.
In use cases of communication based on direct links (or sidelinks), a transmitting (TX) terminal device broadcasts information to surrounding receiving (RX) terminal devices via the direct links, and the RX terminal devices try to detect the broadcast information over all resources. It is required that the RX terminal devices within a certain communication range of the TX terminal devices should be able to detect the information with sufficiently high probability. The information is modulated by the TX terminal device before being broadcasted. As specified in current communication specifications, only some low order modulation schemes such as Quadrature Phase Shift Keying (QPSK) modulation and 16 Quadrature Amplitude Modulation (16QAM) modulation are currently supported for V2X communications.